Simultaneous Measurement of Intracrystalline Diffusion in Molecular Sieve Zeolites by NMR and Gravimetric Methods

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Research Summary: The diffusive and adsorptive properties of hydrocarbons on high-silica zeolites are investigated by gravimetric and NMR methods to resolve the differences in diffusion measurements, which are reported in the literature to be of several orders of magnitude between measurements made by these two techniques, in order to gain fundamental understanding of diffusion in zeolites. Novelty: A new apparatus is being constructed and will be used to make simultaneous diffusion measurements of identical zeolite samples, activated under exactly the same conditions, under identical sorbate pressure, using NMR and gravimetric methods. This unique method of measurement will make it possible to compare the results from microscopic NMR measurements to those from macroscopic gravimetric measurements, thus resolving currently existing large differences. Technical Impact: The information obtained from the proposed work will not only provide fundamental understanding of the transport and adsorption properties of zeolites but also will be of importance in improving engineering design in such important operations as purification of gas streams, separation processes, and catalytic conversion units. A better understanding of the diffusion mechanisms and equilibrium properties can provide valuable information in understanding catalytic behavior of shape-selective zeolites used in practical industrial applications such as xylene isomerization, dewaxing and conversion of methanol to gasoline.